Chemical reactions of everyday life.
Posted on July 3rd, 2011

Dr Hector PereraƒÆ’-¡ƒ”š‚  London

Cooking and many chemical reactions are known to people for long time but let me limit the list for example cooking rice and curries, hoppers, bread, pizza and brewing local beer or toddy, making vinegar or coconut and wine vinegar, making illicit liquors, making cider from apples, home made wine, making yoghurt or curd and many more practical things. When we make Sri Lankan pickles with small red onions, green papaw, carrots, green chilies, mustard, salt, coconut vinegar and a touch of turmeric, usually they keep the contents in closed bottles. This is because for the reactions to take place. How did these ordinary people understand that the reactions have to take place in closed environment? ƒÆ’-¡ƒ”š‚ If we left this pickle mixture in a jar without a lid, would it form a tasty pickle? At the start one cannot eat the green chilies but after two days when it is seasoned, it can be easily tasted. This is because a series of chemical reactions have taken place within the pickle bottle, the sweet smell is unmistakable that is due to esters formed within the bottle.


Sri Lankan pickles

ƒÆ’-¡ƒ”š‚ What about pickled lime, mango and ƒÆ’‚¢ƒ¢-¡‚¬ƒ…-amberallaƒÆ’‚¢ƒ¢-¡‚¬ƒ”š‚? In Sri Lankan wedding dinner parties or during the Sinhalese New Year, these pickles are a must on the dinner table. Apart from that, ƒÆ’‚¢ƒ¢-¡‚¬ƒ…-veralu achachruƒÆ’‚¢ƒ¢-¡‚¬ƒ”š‚ and pineapple ƒÆ’‚¢ƒ¢-¡‚¬ƒ…-achcharuƒÆ’‚¢ƒ¢-¡‚¬ƒ”š‚ are a common sight in church feasts and in Sunday ƒÆ’‚¢ƒ¢-¡‚¬ƒ…-PolaƒÆ’‚¢ƒ¢-¡‚¬ƒ”š‚. In the past, just by the school gates, an old lady with a basin of ƒÆ’‚¢ƒ¢-¡‚¬ƒ…-veralu achcharuƒÆ’‚¢ƒ¢-¡‚¬ƒ”š‚ was a common sight but not any more. We forget for a moment that excess salt is bad for blood pressure.

ƒÆ’-¡ƒ”š‚ The point is, some people know about these day today chemical reactions but why not help to expand their knowledge and educate them a little bit more of the chemicals in a better way.

What happens during cooking?

When we cook, the heat that is absorbed into the vessel by a process of conduction, if more heat is supplied than the thermal capacity of the vessel, then the heat is wasted, further it has bad burning effect on the food. Why some ladies cannot cook rice without burning? Of course they can with a rice cooker, not otherwise? The thermal capacity of the material such as copper, aluminium or stainless steel is that much it can hold, if more heat is supplied, the excess heat is lost by means of radiation. When excess heat gets transferred to the food in the vessel, the molecular vibration and kinetic energy increase further, some get burnt and some get over cooked.

ƒÆ’-¡ƒ”š‚ Temperature of cooking

They must understand the temperature of the gas flame is between 1100 to 800 0C or more and this much of heat is more than enough to cook food. The firewood gives much less temperature than a gas flame. When we cook, some volatile chemicals escape from the food and condense anywhere it comes in contact. I mentioned that some chemicals ƒÆ’‚¢ƒ¢-¡‚¬ƒ…-piggy backƒÆ’‚¢ƒ¢-¡‚¬ƒ”š‚ water molecules and escape. Piggy back water molecules deposit on any surface then water evaporates; leaving those volatile chemicals that is how some oily surface is found near the cooker and the things nearer the cooker. If you happened to be there then some of it is bound to deposit on you.


ƒÆ’-¡ƒ”š‚ Use science for cooking

What I attempt to do is to reduce this chemicals escaping and let it be in the food you cook, no point in wearing this cocktail of smells or ƒÆ’‚¢ƒ¢-¡‚¬ƒ…-Asian cologneƒÆ’‚¢ƒ¢-¡‚¬ƒ”š‚ or ƒÆ’‚¢ƒ¢-¡‚¬ƒ…-Chicken cologneƒÆ’‚¢ƒ¢-¡‚¬ƒ”š‚ on you. Why do we add different spices and cooking ingredients to a chicken curry or a vegetable curry, is it flavour the curry or for you to get a younger look with spicy ƒÆ’-¡ƒ”š‚ herbal vapour bath? The only thing is some people roll up their eye brows as you go pass them due to this odour on you. In their minds they visualize you as a, mobile kitchen but keep the mouth shut to avoid any embarrassment.

No British spices can beat Sri Lankan spices.

We know the roasted curry powder adds more flavour to some food such as chicken and fish and the odour that comes out of this roasted curry powder is very strong and bound to get adsorbed and absorbed on to you for a while. When I say spices, itƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s a mixture of herbs only; chilies may not be always included. I know the odour is very appetising but would you think itƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s a nice smell to wear as an aftershave or cologne? I talked to a few people including a few ladies and they told me, they need to seek the help of sprays and colognes to cover it up. One cannot get rid of this odour even by a wash because it deposits all over the body, including the hair, clothes and jewellery, so the best quick remedy is to seek the help of sprays and colognes but the fact remains the same this ƒÆ’‚¢ƒ¢-¡‚¬ƒ…-curry smellƒÆ’‚¢ƒ¢-¡‚¬ƒ”š‚ is there on you. Let me point out the problem then give you a solution.


Burning effect from Bournemouth to Portsmouth

Any of these spices such cinnamon, cardamom, cloves, nutmeg, corianders, turmeric or cumin powder has to be added in small quantities to make a dish palatable, otherwise it goes tasteless. Very often, I have noticed some so called British TV celebrity cooks; just add anything because they assume the people would accept them for whatever they do, including swearing four letter words. If we add too much one thing for example 10 or 15 pieces of cloves to a kilo of chicken and a two or three long sticks of cinnamon, they can definitely give a nasty taste and if someone tried to eat then, eventually it will have a bad effect in the stomach. It will give a burning sensation from Bournemouth to Portsmouth, I am sure you know what I mean? If you donƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢t believe me just try and let me know. This excess spice upsets the reactions of the digestive juices and interferes with digestion, leading to indigestion. Cooking something is different to eating and enjoying the food. WhatƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s the point of cooking something if it cannot be eaten and enjoyed? This is just one excess ingredient, what about any other, they also have the same effect. Excess chilies, salt, vinegar or even lime juice can upset the actual taste of the food, so be careful about the amounts to be added, this comes with experience or try and learn by mistakes.

When the opportunity arises to demonstrate how to cook scientifically, I am happy to help the nation save gas, save money and help cut down some environmental pollution. Why not our scientists, educate the people about chemical reactions of everyday life? How about some comments,

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